1. Field of the Invention
The present invention relates to a computer-controlled telecommunications system and, in particular, to control circuitry for establishing an optimum communications link between a transmitter device and a receiver device.
2. Description of the Related Art
Recent advances in technology have resulted in unprecedented growth and diversification in the field of telecommunications. Telecommunications systems, long used for transmitting voice signals between telephones, are now being implemented in a wide variety of other applications. Such applications include, for example, the transfer of information between local area networks (LANs) and the transmission of documents via facsimile. The wide variety of available telecommunications applications has resulted in a marked increase in the use of telecommunications systems.
Telecommunications system use has also increased as a result of the greater number of telephone devices now available. With the advent of devices such as portable and cellular telephones, more people spend a greater amount of time in telephonic communication than in the past.
These factors have contributed to a general increase in the use of telecommunications systems and, in particular, to an increase in the use of telecommunications systems for sending long distance and international transmissions. The dramatic social and economic changes which the world has undergone in the past several years have also resulted in the increased use of long distance and international telecommunications systems. The current socioeconomic climate of the world suggests that the number of long distance and international transmissions will continue to grow at an increased rate.
The major drawback associated with long distance and international telecommunications system use is cost. Each time a long distance or international telephone call is made, a charge is imposed by a telecommunications carrier such as MCI or AT&T. The amount of the charge depends on (1) the telecommunications carrier used, (2) the time of the call, and (3) the telecommunications charge zone from which the call originated. In general, telecommunications charges for a given charge zone are highest during the day (standard charges), somewhat lower in the early evening (discount charges), and lowest during the late evening and early morning hours (economy charges).
Various systems have been proposed to reduce the cost of long distance telephone calls. One of these systems is depicted in FIG. 1.
The system of FIG. 1 includes a telephone 1 which a user such as a person may use for making long distance telephone calls to a receiver telephone 2. Telephone 1 is coupled to a dialer box 3 owned by an operating company. The dialer box is used to dial the telephone number of a card 4 owned by the same operating company that owns the dialer box. Dialer box 3 dials the telephone number of the card 4 each time the user dials a long distance telephone number into telephone 1.
The user of telephone 1 rents the dialer box 3 and the card 4 from the operating company. Dialer box 3 and telephone i are located in a facility outside of the United States. Card 4 is located within the United States.
To place a call to the receiver telephone 2, the user places telephone 1 in the "off hook" state and then dials the telephone number of the receiver telephone. Telephone 1 provides the telephone number of the receiver telephone to dialer box 3 which, in response, dials the number of the card 4. Card 4 then returns a signal to telephone 1, at which time the user places telephone 1 in the "on hook" state and waits for a call from the card.
Card 4 then dials the number of telephone 1, causing telephone 1 to ring. When telephone 1 rings, the user again places telephone 1 in the "off hook" state, thereby establishing a transmitter communications path between card 4 and telephone 1.
Next, card 4 dials the telephone number of receiver telephone 2, causing the receiver telephone to ring. When receiver telephone 2 is placed in the "off hook" state, a receiver communications path is established between the card 4 and the receiver telephone.
Card 4 then establishes a communications link between telephone 1 and receiver telephone 2 through the transmitter and receiver communications paths, which allows the transmission of voice signals between such telephones. Because the communications link is established by card 4 rather than by telephone 1, the telecommunications charge incurred by the user is associated with the charge zone of the card instead of the charge zone of telephone 1.
Another approach to reducing long distance charges is shown in FIG. 2. The system of FIG. 2 includes a telephone 5 coupled to a digital switch 6 which comprises a line card 7, a dedicated trunk card 8, and central processing unit (CPU) 9 having an associated memory unit 10. Line card 7 has several line ports 11 for coupling to telephone lines. Trunk card 8 has several trunk ports 12 which are each coupled to a telephone line owned by a common carrier such as MCI or AT&T.
When a user at telephone 5 wishes to place a call to a receiver telephone (not shown), the user places telephone 5 in the "off hook" state and dials the number of the receiver telephone. The call from telephone 5 is received by digital switch 6 through one of line ports 11. Digital switch 6 then routes the call to the receiver device through a selected trunk port 12 using the telecommunications carrier telephone line coupled to that trunk port.
The system of FIG. 2 performs a least cost routing (LCR) function. The LCR function determines which telecommunications carrier telephone line, if used, will result in the lowest telecommunications charge. The LCR function then selects the trunk port which is coupled to that line for use as the trunk port for routing the call to the receiver device. If the selected trunk port is available, the call is routed to the receiver device from the selected trunk port. If the selected trunk port is unavailable, the LCR function is repeated until an available trunk port is selected.
The systems of FIGS. 1 and 2 are deficient for a variety of reasons. The system of FIG. 1, for example, only accepts calls from outside of the United States. As a result, users within the United States cannot use such a system to reduce long distance or international transmission charges. Moreover, the system of FIG. 1 requires the rental of the dialer box 3 and card 4 at a rate of approximately two hundred dollars per month. Also, this system is subject to both level matching and line balancing problems.
In addition, the system of FIG. 1 is a proprietary hardware-based system which only accepts calls from those user telephones that are connected to dialer boxes. As a result, users of this system are severely limited in the options available for accessing the system. Each user can only access the system using the telephone coupled to that user's dialer box. If a user is not near a telephone that has already been connected to a dialer box, then that user cannot access the system.
Furthermore, the hardware-based nature of the system of FIG. 1 limits its flexibility and utility. The basic function performed by card 4 is to establish a communications link between the telephone 1 and receiver telephone 2. Card 4 cannot be programmed or controlled to perform other useful functions such denying access to a user when that user's credit status is unsatisfactory, or determining whether placement of a call through the card will actually result in decreased charges for the user.
An additional shortcoming of the system of FIG. 1 is that users always incur a telecommunications charge associated with the telecommunications charge zone in which the card 4 is located. More often than not, this charge is not the lowest telecommunications charge available. Numerous other telecommunications charge zones may have lower charges, but the system of FIG. 1 does not recognize or take advantage of these lower charges.
In addition, when the telecommunications charge associated with the charge zone in which the card 4 is located is higher than the telecommunications charge associated with the charge zone in which telephone 1 is located, the system of FIG. 1 cannot even be used without causing a higher charge than if a direct call were placed from telephone 1 to receiver telephone 2, which is a severe and costly limitation associated with the system of FIG. 1.
Like the system of FIG. 1, the system of FIG. 2 does not recognize or take advantage of the fact that at various times throughout each day, different telecommunications charge zones provide lower available charges. The system of FIG. 2 is merely an intra-switch mechanism which compares charges imposed by various telecommunications carriers to select one of the carriers. The system of FIG. 2 does not reduce costs by establishing communications links using switches located in different telecommunications charge zones. In the system of FIG. 2, communications links between telephone 5 and the receiver telephone are always established in the telecommunications charge zone in which digital switch 6 is located.